The determination of the presence, type, and number of parasites is relevant to human and animal health. In particular, the detection of parasite eggs can indicate an undesirable parasitic infection in the human or animal host. Microscopy is commonly used to detect, identify, and count parasite eggs within different materials, especially biological materials that include: feaces; drinking water; waste water; soil; blood; and food for example.
It may also be important to determine the presence, type, and number of other particles in materials such as water, soil, and food to assess contamination of the material. For example, the presence, type, and number of pollen particles in a sample of soil may be used in scientific or archaeological studies. Similarly, the presence, type, and number of pollen particles in honey may be used to determine the type of honey.
Consequently, various apparatus and methods have been developed that use microscopy for detecting, identifying, and counting sub-millimeter scale particles within material suspended in a fluid sample, such particles including pollen and parasite eggs for example.
However, a difficulty associated with the microscopic analysis of some materials in fluids is that the particles tend to be positioned throughout the fluid and also tend to move within the fluid. As a result, the particles do not accumulate or remain within the same microscopic field of view or within a common focal plane. The microscope operator is, therefore, required to translate the microscope and adjust its focal point to view all particles dispersed throughout the sample.
One known device and method of particle analysis has attempted to overcome this difficulty by providing for a sample of the particles to be examined on a microscope slide called a McMaster slide. The slide includes upper and lower transparent plates with a cavity between. This device and method requires the use of a compound optical microscope. In this form of particle analysis, the buoyant particles float to the surface of a dense fluid sample. A sample of the fluid is taken and placed within the cavity of the slide. The particles in the slide are substantially immobilised and fixed within a common focal plane as a result of buoyant forces and the upper plate of the slide. An operator uses a microscope to manually observe and identify the particles. However, the device and method do not bring the particles within a single microscopic field of view. Thus, the area of the slide that can be simultaneously observed is limited so it becomes necessary for the microscope operator to continually translate the microscope over the slide to detect and/or identify and/or count particles on the slide. Also, the slide must be handled with great care to prevent the contents of the slide from spilling out.
Another method and device specifically used for the detection, identification, and/or counting of parasite eggs from the faecal stool samples of agricultural livestock and humans is called FLOTAC (see Cringoli et al., “FLOTAC: New multivalent techniques for qualitative and quantitative copromicroscopic diagnosis of parasites in animals and humans”, Nature Protocols, 5, 503-515, 2010). The FLOTAC device and method can be used to analyse the presence of helminth parasites in the stool specimens of various species of animals, including humans, by providing for the detection, identification, and/or counting of parasite eggs in the stool specimens.
However, each of these known devices and methods for particle detection, identification, and analysis exhibit a number of disadvantages.
One disadvantage is that the presence of pigments and debris in the fluid samples limits the depth of the sample that can be analysed, due to the difficulty of viewing particles in such samples.
Another disadvantage is that only operators with a sufficient level of competency can carry out the analysis using such sophisticated devices as compound optical microscopes, thereby often limiting the analysis to a laboratory environment.
Yet another disadvantage is that the field of view offered by a compound optical microscope (operated at sufficient magnification to enable particle detection, identification, and counting), limits the area that can be simultaneously observed and, therefore, requires the microscope operator to translate the field of view over a specified area of the sample.
The process of manual translation of the microscope is time-consuming, adding to the cost of the analysis. Translation also introduces vibrations which may lead to inaccuracies in the analysis of particles. In addition, the prolonged viewing of a moving image causes eye strain and fatigue, and repeated manual operations of adjustment can cause repetitive strain injury (RSI).
Furthermore, it is desirable to be able to audit the raw data and analysis of the image data because of the risk of misidentification. Such permanent records often take the form of optical photomicrographs, which can be procured in a digital format and allow for their electronic storage and communication. However, the requirement for translation diminishes the practicability of recording the microscope image data because multiple overlapping image frames must be captured and stored in order to view the whole slide.
Thus, there is a need to provide an apparatus and method for the microscopic analysis of particles in fluids that: (a) positions the particles in a common focal plane; (b) reduces the need to translate the microscope to view the sample; (c) mitigates the effects of pigmentation and extraneous debris; (d) improves the practicability of providing a permanent record of the microscope image data; (e) can be operated outside of a laboratory by relatively unskilled people; or (f) at least provides the public with a useful alternative.